The present invention relates to an ultrasonic welding apparatus including an ultrasonic horn for holding an engagement portion of a plastic fastener such as a plastic stud or a plastic clip, the plastic fastener having a flange to be welded onto a workpiece and the engagement portion extending from the flange, wherein the flange of the plastic fastener held by the ultrasonic horn is brought into contact with workpiece and ultrasonic energy is applied to the ultrasonic horn so that the plastic fastener is ultrasonically welded onto the workpiece. The present invention further relates to an ultrasonic welding method for a plastic fastener.
It is already commonly practiced to weld, by using ultrasonic energy, a plastic fastener such as a plastic stud or a plastic clip which has a flange to be welded onto a workpiece such as a plastic panel and an engagement portion extending from the flange. One known ultrasonic welding apparatus includes an ultrasonic horn for holding the engagement portion of the plastic fastener, and means for bringing the flange of the fastener held by the ultrasonic horn into contact with the workpiece, wherein ultrasonic energy is applied to the ultrasonic horn so that the flange of the plastic fastener is welded onto the workpiece.
In a conventional ultrasonic welding apparatus, an engagement portion of the plastic fastener is manually inserted into the tip of the ultrasonic horn so that the ultrasonic horn can hold the engagement portion of the plastic fastener. Alternatively, in the case of automatic loading, the ultrasonic horn is moved to a location where the plastic fastener has been fed for loading there. However, as it is troublesome to load the fasteners one by one, such loading operations are not efficient. Particularly, for loading a plastic fastener to the ultrasonic horn, it is necessary to securely locate the engagement portion of the plastic fastener in the tip of the ultrasonic horn. In order to make manual loading quickly, it is also necessary to master such a skill. In automatic loading, the mechanism for moving the ultrasonic horn may become complex.
Therefore, it is an object of the present invention to provide an ultrasonic welding apparatus of a simple structure that allows automatic loading of a plastic fastener to an ultrasonic horn, and to provide an ultrasonic welding method with high efficiency in its operation.